Attached Link: http://www.lysator.liu.se/~kand/caustics/

Check out this link. It's a freebie stand-alone mini-app, that produces pics that imitate the way light looks after going through water and hitting some surface (caustics). Open output in Photoshop, select and copy-paste it onto a new layer in your pic, and mask to apply it to (for example) the ocean floor, or (lightly) onto the fish themselves.

RosemaryR
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"This...this is magnificent!"
"Oh, yeah. Ooooo. Aaaaah. That's how it starts.
Then, later, there's ...running. And....screaming."